/**
 * 
 * NOTICE -- YOU MUST LEAVE THIS NOTICE IN PLACE.  PER THE TERMS OF THE LICENSE BELOW, YOU MAY SUBLICENSE THIS SOFTWARE 
 * IN ANY WAY THAT DOES NOT CONFLICT WITH THIS LICENSE.
 *
 * Copyright (c) 2011, Paul Gribben <paul.gribben@gmail.com>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the 
 *       documentation and/or other materials provided with the distribution.
 *	
 *	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
 *	INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 *	DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
 *	SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
 *	WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
 *	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
package org.softwise.rss2kindle.impl;

import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.xml.transform.Transformer;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.sax.SAXSource;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.ccil.cowan.tagsoup.Parser;
import org.softwise.rss2kindle.model.RssEntryTransformer;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;

public class HtmlRssEntryTransformer implements RssEntryTransformer {
	private final XPath xpath = XPathFactory.newInstance().newXPath();
	private final String xpathFilter;
	private final XMLReader reader = new org.ccil.cowan.tagsoup.Parser();
	private final Transformer transformer;
	
	public HtmlRssEntryTransformer(final Transformer transformer,
			final String xpathFilter)
			throws Exception {
		reader.setFeature(Parser.namespacesFeature, false);
		reader.setFeature(Parser.namespacePrefixesFeature, false);

		this.xpathFilter = xpathFilter;
		this.transformer = transformer;
	}
	
	@Override
	public List<RssEntry> getEntries(RssEntry syndEntry) throws Exception {
		URL linkUrl = new URL(syndEntry.getLink());
		Reader urlReader = new InputStreamReader(linkUrl.openStream(), "UTF-8");
		DOMResult result = new DOMResult();
		transformer.transform(
				new SAXSource(reader, new InputSource(urlReader)), result);
		Node docNode = result.getNode();
		NodeList elements = (NodeList) xpath.evaluate(xpathFilter, docNode,
				XPathConstants.NODESET);
		
		List<RssEntry> rssEntries = new ArrayList<RssEntry>();
		
		for (int i = 0; i < elements.getLength(); i++) {
			Element currElem = (Element)elements.item(i);
			RssEntry newEntry = createRssEntry(currElem);
			if (newEntry != null) {
				rssEntries.add(newEntry);
			}
		}
		
		return rssEntries;
	}

	private RssEntry createRssEntry(Element elem) {
		String title = elem.getParentNode().getTextContent();
		String link = elem.getAttribute("href");
		if (link != null && title != null) {
			return new RssEntryImpl(title, link);
		} else {
			return null;
		}
	}
}
